I have posted this one before. Other then modern MLB authenticated balls this is the only game used ball currently in my collection. Although I feel confident about the provenance, I purchased it from "John" the gentleman who caught the ball and had it signed after the game, I don't believe anyone can be certain about such items.
Ironically a close friend of mine is the brother-in-law of Todd McFarlane who as you know purchased McGwire's #70 HR ball for 2.7 million.
http://www.teako170.com/70th.html I asked my friend how McFarlane justified spending that kind of money especially in light of the steroid issue that has tarnished McGwire's accomplishment. He said that the ball was purchased for the publicity. He said the amount and value of free prime time network and print media advertising it brought to McFarlane's company far exceeded the amount of money spent on it. When the steroid scandal gained national attention the ball's and it's owner were in the news all over again.